Europe’s flora is becoming impoverished

And thereby losing the ability to react to environmental changes

Halle/Saale. With increasing species richness, due to more plant introductions than extinctions, plant communities of
many European regions are becoming more homogeneous. The same species are occurring more frequently, whereas rare species
are becoming extinct. It is not only the biological communities that are becoming increasingly similar, but also the
phylogenetic relations between regions. These processes have led to a loss of uniqueness among European floras,
scientists from the DAISIE research project have published their findings in the current online edition of the
scientific journal Proceedings of the National Academy of Sciences of the USA (PNAS).

Originally, the Oregon Holly Grape (Mahonia aquifolium) is from the Pacific Northwest of United States of
America. For their colourful flowers the evergreen shrub was quickly cultivated and spread by gardeners in Europe.
Photo: André Künzelmann/UFZ

For their research the scientists analysed the data of flora native to Europe (Flora Europaea), extinct plant species (national red lists)
and alien plant species from the DAISIE database (www.europe-aliens.org). About 1,600 new non-European species were introduced to the
approx. 11,000 native European plant species since 1500 A.D. The researchers also took into account those European plants that are
native to a particular region of Europe but considered as introduced species in another (approx. 1,700. It works in a similar way for
the species considered to be "extinct". While in the whole of Europe only 2 plant species can "really" be considered as extinct,
approx. 500 species have become locally extinct. One such example is the Blue Woodruff (Asperula arvensis), a weed that grows on
cultivated land, which has been greatly displaced particularly from the intensification of agricultural practices. This species is
considered to be locally extinct in Germany and Austria for example, whereas it still occurs e.g. in Italy and Spain.

The researchers were able to demonstrate, that biodiversity is increasing in all regions of Europe due to high numbers of alien species.
But at the same time the plant communities of the regions are becoming increasingly more homogenous because alien species are
distributed relatively consistently over the continent. The remarkable thing is that it is not only the diversity between plant
communities that is decreasing (taxonomic homogenisation), but also the phylogenetic diversity.. Phylogenetic diversity reflects
the evolutionary history of a community and therefore also its genetic diversity, which can also be an expression of its functional
diversity. A phylogenetic tree with high diversity can be imagined as a genealogical tree with a protruding crown, with many strong
branches (distantly related species) and numerous twigs (many species). A high phylogenetic and taxonomic diversity (many tree species
that look different), presents a wealth of information and ability, making it possible for biological communities to react to
environmental changes, like those arising for example from the current global climate change (e.g. climate or land use change). If one
finds many very similar looking trees, then one assumes that the flexibility of the communities is no longer as high to be able to react
positively to these changes. Put simply: the genealogical tree of the plant species occurring in Europe has got more twigs, but these only
sprout from a few large branches.

Biological depletion from loss of species and introduced species is a consequence of global change associated with increasing pressure
on the environment (e.g. the intensification of agriculture, the loss of habitat diversity, urbanisation, increasing global traffic and
excessive nutrient influx into ecosystems).

"Our studies have shown that in spite of an increase in regional species richness due to species introductions exceeding the local
extinctions of plant species in European regions, these are increasingly losing both their phylogenetic and taxonomic uniqueness",
according to Dr. Marten Winter from the Helmholtz Center for Environmental Research (UFZ). "In all discussions on `biodiversity’ one needs to
consider other forms of biodiversity than pure species richness e.g. those of phylogenetic relations. These can supply additionally
important information about the condition and possible risks to ecosystems ", the researcher adds.

Over the last few years, the EU project DAISIE (Delivering Alien Invasive Species Inventories for Europe) has gathered for the first
time information on all known alien species across Europe. Information on the ecology and distribution of alien plant and animal species
was collected and has been made available for interested parties via an Internet database. Research institutes and organizations from
15 nations were involved in the project.

At the Helmholtz Centre for Environmental Research (UFZ) scientists research the causes and consequences of far-reaching environmental
changes. They study water resources, biological diversity, the consequences of climate change and adaptation possibilities, environmental and
biotechnologies, bio energy, the behaviour of chemicals in the environment and their effect on health, as well as modelling and social
science issues. Their guiding research principle is supporting the sustainable use of natural resources and helping to secure these
basic requirements of life over the long term under the influence of global change. The UFZ employs 930 people at its sites in Leipzig,
Halle and Magdeburg. It is funded by the German government and by the states of Saxony and Saxony-Anhalt.

The Helmholtz Association helps solve major, pressing challenges facing society, science and the economy with top scientific
achievements in six research areas: Energy, Earth and Environment, Health, Key Technologies, Structure of Matter, Transport and Space.
With 28,000 employees in 16 research centres and an annual budget of around EUR 2.8 billion, the Helmholtz Association is Germany’s
largest scientific organisation. Its work follows in the tradition of the great natural scientist Hermann von Helmholtz (1821-1894).